From 4c81f9e5a2e28eddd632831c1dc502eb48fce617 Mon Sep 17 00:00:00 2001
From: mlemanczyk <marek@lemanczyk.eu>
Date: Thu, 16 Oct 2025 21:21:40 +0200
Subject: [PATCH] IsPrime cache reused

---
 PerfectNumbers.Core/PrimeOrderCalculator.cs | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/PerfectNumbers.Core/PrimeOrderCalculator.cs b/PerfectNumbers.Core/PrimeOrderCalculator.cs
index fc4b039..68fe8a9 100644
--- a/PerfectNumbers.Core/PrimeOrderCalculator.cs
+++ b/PerfectNumbers.Core/PrimeOrderCalculator.cs
@@ -906,7 +906,12 @@ internal static partial class PrimeOrderCalculator
 		for (int i = 0; i < pendingCount; i++)
 		{
 			ulong composite = pending[i];
-			bool isPrime = Open.Numeric.Primes.Prime.Numbers.IsPrime(composite);
+			if (!primalityCache!.TryGetValue(composite, out bool isPrime))
+			{
+				// Console.WriteLine($"Checking composite {composite}");				
+				isPrime = Open.Numeric.Primes.Prime.Numbers.IsPrime(composite);
+				_ = primalityCache.TryAdd(composite, isPrime);
+			}
 			if (isPrime)
 			{
 				AddFactorToCollector(ref useDictionary, ref counts, primeSlots, exponentSlots, ref factorCount, composite, 1);